The present invention relates in general to a device or system for altering an electrical audio signal. More particularly, the present invention relates to an electronic processing device preferrably used with the bass guitar for producing controlled distortion of the audio output signal and for providing controlled enhancement of the tonal quality of the audio signal.
There are many prior art devices available which alter the tonal quality of electrical audio signals. For example, one prior art device has a distortion generator or a distortion compressor stage followed by a filter with a roll-off or attenuation with increased frequency, along with means to adjust either the amount (steepness) of the roll-off, or the point (knee) of the roll-off. However, the filter in such a device is very crude. Further, the adjustment means requires the operator to experiment with different settings or combinations of settings in order to define a desirable sound, and even then the device is limited in the quality of sound which it is capable of producing. Moreover, the arrangement just described does little if anything to tailor or enhance the character or quality of the tone of the signal produced by the distortion generator or compressor stage.
Reference is also made to co-pending application Ser. No. 420,280 filed Sept. 20, 1982, now U.S. Pat. No. 4,584,700, which describes an improved electronic audio signal processor. It is the purpose of the present invention to provide a circuit having some of the characteristics of this prior circuit but adapted in particular for use with a bass guitar.
Accordingly, it is an object of the present invention to provide an improved electronic audio signal processor system that is adapted to alter and improve the total quality of the audio signal.
Another object of the present invention is to provide an improved electronic audio system that is in particular adapted for use with a bass guitar or similar instruments having substantial low end audio signal content.
A further object of the present invention is to provide an electronic audio system in accordance with the preceeding objects and which also has means for providing controlled distortion of the audio signal.
A further object of the present invention is to provide an improved electronic audio signal system having means for controlling such parameters as sustain and attack.
To accomplish the foregoing and other objects, advantages and features of the invention, there is provided an electronic audio signal system for processing signals in the audio frequency range and comprising an input circuit means for receiving the audio signal. This input circuit means comprises a compressor and a detector means which is preferrably an RMS detector. The use of an RMS detector circuit is in particular compatible with a musical instrument such as a base guitar. The use of an RMS detector overcomes previous problems associated with the use of a peak detector. The compressor preferrably comprises a compressor operational amplifier. The input circuitry also includes a sustain control switch means and it is preferred that there be provided a feedback loop between the input and output of the compressor op amp including in the feedback loop the RMS detector and a pole of the sustain switch. The system of the invention also comprises a filter means comprising separate high EQ, mid EQ and low EQ filter circuits. The high EQ circuit comprises a plurality of separate filters. Similarly, the low EQ filter circuit comprises a plurality of separate filter circuits. There is also provided an EQ switch means coupled from the output of the low, mid and high frequency filter circuits for selectively establishing multiple frequency response wave forms. The EQ switch means preferrably has three positions and has its output coupled to a mixer circuit. There is also provided a volume control switch at the output of the aforementioned mixer.
In accordance with one feature of the present invention there is provided a high frequency compressor in addition to the input compressor circuit. The high frequency compressor has associated therewith a compressor switch for providing improved operation.
In accordance with another feature of the present invention there is provided peak clipping circuitry for providing instantaneous limiting. Clipping circuitry is used to remove transients above a predetermined threshold.
In accordance with another feature of the present invention thee is provided an improved chorus circuit which there is provided selective frequencies by means of separate filters along with a preferred inverter arrangement adapted to limit the amount of low frequency phase shift. This makes it easier to record on phonographic discs.